Comet orbiting a Star - True and False

Consider the path of a comet orbiting a star, the system of the comet plus the star. Which of the following statements are correct?

Select all that are True.
1) As the comet slows down, the kinetic energy of the system decreases.
2) As the comet's kinetic energy increases, the gravitational potential energy of the system also increases.
3) External work must be done on the system to speed up the comet.
4) As the kinetic energy of the system increases, the gravitational potential energy of the system decreases.
5) As the comet slows down, energy is lost from the system.

The effect of gravity is taken into consideration by the potential energy of the comet-star system.
That is the total mechanical energy can only be changed if another force, other than gravitational attraction, comes into play.